Submersible pumping systems are often deployed into wells to recover petroleum fluids from subterranean reservoirs. Typically, the submersible pumping system includes a number of components, including one or more fluid filled electric motors coupled to one or more high performance pumps located above the motor. When energized, the motor provides torque to the pump, which pushes wellbore fluids to the surface through production tubing. Each of the components in a submersible pumping system must be engineered to withstand the inhospitable downhole environment.
Components commonly referred to as “seal sections” protect the electric motors and are typically positioned between the motor and the pump. In this position, the seal section provides several functions, including transmitting torque between the motor and pump, restricting the flow of wellbore fluids into the motor, protecting the motor from axial thrust imparted by the pump, and accommodating the expansion and contraction of motor lubricant as the motor moves through thermal cycles during operation.
Prior art seal sections typically include a “clean side” in fluid communication with the electric motor and a “contaminated side” in fluid communication with the wellbore. Bellows or bags have been used to separate the clean side of the seal section from the contaminated side. Although generally effective, prior art designs rely on the communication of fluid between the motor and the seal section. Because the lubricant is common to both the motor and the seal section, the same fluid must be used. It is to this and other restrictions in the prior art that the preferred embodiments are directed.